Large signs, typically referred to as billboards, are located along the vast majority of roadways in the United States and many other countries. The signs typically carry advertising directed at the individuals passing by the sign. Because most of the billboards are located outdoors, they are exposed to wind damage during storms. The damage can be caused by the force of the wind alone, as well as from flying debris.
These structures are typically designed to withstand winds of 70-110 mph. In some locations, particularly those prone to hurricane-force winds, those structures are not adequate to prevent damage and/or destruction of the billboard and support frame during a hurricane, as winds can reach levels of 165 mph or greater. As a result, billboards in such areas are periodically destroyed as storms move through the areas.
The damage to billboards can be roughly separated into damage to the sign face itself, i.e., the portion of the billboard carrying the advertising message. Alternatively, the frame supporting the sign face and the support structure used to elevate the frame above the ground to facilitate viewing of the sign face can be damaged by the wind. In some instances, damage will be only to the sign face, leaving the frame and support structure intact. In other cases, the sign face and frame may be damaged, while the majority of the support structure remains in place. In the worst case scenario, the sign face, frame and support structure are all destroyed due to the force of the wind.
Because the sign face presents a relatively large surface area to the wind, as opposed to the frame and support structure, it is typically the root source of the damage to both the frame and support structure, particularly where the sign face is sturdy enough to transmit large portions of the wind energy to the frame and support structure before losing enough surface area to reduce the forces transmitted to the frame and support structure.
Loss of the frame and/or support structure can cause severe consequences. Many localities attempt to control/reduce the number and location of billboard signs by preventing owners from erecting new signs in place of those whose frame and/or support structure have been damaged beyond repair. Many of those locations are highly desirable due to traffic flow and other considerations. As a result, the owner can face a significant economic loss if the sign frame and support structure are damaged beyond repair and cannot be replaced, as that location will be lost for future advertising revenues.
As a result, many billboard owners resort to removing the panels of signs in the probable path of storms. That practice is, however, labor intensive, as well as being limited to those signs which are reached by removal crews before wind speeds exceed safe levels. In addition, the paths of many storms are not accurately predicted, resulting in the removal of signs which would have been safe and the failure to remove sign panels which are subsequently destroyed in the storms.
Attempts have been made to design billboard signs which minimize wind damage. Those attempts have included hinging the panels making up the sign face to allow them to rotate in response to wind forces. That design, however, suffers from a number of problems. First, it is difficult to construct a sign with rotatable panels which is aesthetically pleasing--an important consideration for signs carrying advertising material. Second, even though the sign is designed to rotate when the wind exceeds a predetermined force, the friction of air flowing over the surface of the hinged panels can provide enough force to damage the panels and/or the supporting frame and support structure in some instances. Finally, those designs are not compatible with the flexible sign faces being used on many billboards.
Another collapsible design includes hinged panels, the ends of which are guided into channels located at opposing side edges of the sign. When the sign is lowered, the panels are removed from the channels and stacked on the ground. Each of the sections or panels are located in a single plane when vertical. As a result, if high winds are being experienced when the sign is being lowered, it may be difficult and/or impossible to lower the sign, as the wind force may prevent the hinges from operating as desired. In addition, the sign is lowered only under force of gravity, which can increase the problems associated with lowering the sign during high winds. Furthermore, the design of the structure requires manual alignment of the sections in the channels at either end of the sign, thereby negating any opportunity to automate raising and lowering of the sign.